Control device for vehicle and control method of vehicle

ABSTRACT

A control device includes an electronic control unit executes steering control for avoiding a collision with an object that has a possibility of colliding with a host vehicle. The electronic control unit sets a timing when the host vehicle is predicted to pass the object as an end timing of the steering control when the steering control is performed. The electronic control unit determines whether or not a deviation possibility is present when the electronic control unit assumes that the steering control ends at the end timing. The deviation possibility is a possibility of the host vehicle deviating from a current traveling lane accompanying an end of the steering control. The electronic control unit performs reduction processing that reduces the deviation possibility when the electronic control unit determines that the deviation possibility is present.

INCORPORATION BY REFERENCE

This application is a continuation of U.S. application Ser. No.16/037,545 filed Jul. 17, 2018 (allowed), which claims priority fromJapanese Patent Application No. 2017-167011 filed Aug. 31, 2017. Theentire disclosures of the prior applications are considered part of thedisclosure of the accompanying continuation application, and are herebyincorporated herein by reference in its entirety.

BACKGROUND 1. Technical Field

The disclosure relates to a control device for a vehicle and a controlmethod of the vehicle.

2. Description of Related Art

Japanese Unexamined Patent Application Publication No. 2015-155295(JP2015-155295A) discloses a vehicle control device that performssteering control when a vehicle passes a pedestrian. The vehicle controldevice identifies the pedestrian close to the vehicle using anon-vehicle sensor. The vehicle control device calculates a collisionprobability with an identified pedestrian and compares the calculatedprobability with a threshold value. When the collision probability withthe pedestrian is higher than the threshold value, the vehicle controldevice sets a separation distance from the identified pedestrian withina current traveling lane. Steering control is control for adjusting aposition of the vehicle in the right and left direction (vehicle widthdirection) when the vehicle passes the identified pedestrian based onthe set separation distance. With the steering control as describedabove, it is possible for the vehicle to safely pass the identifiedpedestrian while the vehicle avoids the collision with the identifiedpedestrian. In the steering control, an adjustment for returning theposition of the vehicle in the right and left direction to the center ofthe current traveling lane is also performed after the passing of theidentified pedestrian ends.

SUMMARY

The steering control described above can be ended at a stage where thevehicle passes the identified pedestrian. That is, the adjustment forreturning the position of the vehicle in the right and left direction tothe center of the current traveling lane can be omitted. With thesteering control as described above, it is possible to minimize anintervention of a driver in a driving operation and to further reduce asense of discomfort felt by the driver during the intervention.

However, when the steering control ends at the stage where the vehiclepasses the identified pedestrian, steering torque generated in thevehicle at the passing stage, a steering angle of the vehicle at thepassing stage, and the like may cause a problem. That is, when thesteering torque is generated in the vehicle at the passing stage, thesteering torque is needed to be maintained by the driver after thesteering control ends. The steering angle of the vehicle at the passingstage is also the same, and the steering angle is needed to bemaintained by the driver after the steering control ends. However, whenthe driver does not grasp the need to maintain the steering angle, thereis a possibility that the vehicle advances in a direction not intendedby the driver and deviates from (depart from) the current traveling laneafter the steering control ends.

The disclosure provides a control device for a vehicle and a controlmethod of the vehicle capable of suppressing the deviation of a vehiclefrom a current traveling lane accompanying the end of steering controlafter the vehicle passes an obstacle in the control device and thecontrol method that performs the steering control when the vehiclepasses the obstacle that has a possibility of colliding with thevehicle.

A first aspect of the disclosure relates to a control device for avehicle. The control device includes an electronic control unit that isconfigured to execute steering control for avoiding a collision of ahost vehicle with an object that has a possibility of colliding with thehost vehicle (hereinafter, referred to as “object”). The electroniccontrol unit is configured to set a timing when the host vehicle ispredicted to pass the object as an end timing of the steering controlwhen the steering control is performed. The electronic control unit isconfigured to determine whether or not a deviation possibility ispresent when the electronic control unit assumes that the steeringcontrol ends at the end timing. The deviation possibility is apossibility of the host vehicle deviating from a current traveling laneaccompanying an end of the steering control. The electronic control unitis configured to perform reduction processing that reduces the deviationpossibility when the electronic control unit determines that thedeviation possibility is present.

According to the above mentioned configuration, in a case where thetiming when the host vehicle is predicted to pass the object is set asthe end timing of the steering control, the reduction processing isperformed when the deviation possibility is determined to be present.Accordingly, the deviation from the current traveling lane accompanyingthe end of the steering control after passing of the object can besuppressed.

In the control device according to the first aspect of the disclosure,the reduction processing may include processing of postponing the endtiming, processing of setting a control amount of steered wheels of thehost vehicle during postponement of the end timing, and processing ofsetting a control amount for causing the host vehicle to travel along atrajectory that maintains a distance from a boundary line on a deviationside of the current traveling lane to the host vehicle to be equal to orlarger than a predetermined distance.

According to the above mentioned configuration, the reduction processingincluding the processing of postponing the end timing of the steeringcontrol and the processing of setting the control amount of the steeredwheels during the postponement of the end timing is performed. In thesetting processing described above, the control amount for causing thehost vehicle to travel along the trajectory that maintains the distancefrom the boundary line on the deviation side of the current travelinglane to the host vehicle to be equal to or larger than the predetermineddistance is set. Accordingly, the deviation of the host vehicle from thecurrent traveling lane can be suppressed with a high probability.

In the control device according to the first aspect of the disclosure,the electronic control unit may be configured to notify a driver of endnotice of the steering control through an interface of the host vehicleduring a period from a timing before the end timing by a predeterminedtime to the end timing. The reduction processing may include processingof notifying the driver of the end notice during a period from thetiming before the predetermined time to a timing after the postponementof the end timing.

According to the above mentioned configuration, the reduction processingthat notifies the driver of the end notice of the steering controlduring the period from an initial notification timing to the end timingafter the postponement of the steering control is performed.Accordingly, a period for preparing the driver for the end of thesteering control can be ensured, and delivery of steering initiativefrom the control device to the driver can be safely performed.

In the control device according to the first aspect of the disclosure,the electronic control unit may be configured to notify a driver of endnotice of the steering control through an interface of the host vehicleduring a period from a timing before the end timing by a predeterminedtime to the end timing. The reduction processing may include processingof notifying the driver of the end notice during a period from a timingfurther earlier than the timing before the predetermined time to the endtiming.

According to the above mentioned configuration, the reduction processingthat notifies the driver of the end notice of the steering controlduring the period from a timing further earlier than the initialnotification timing to the end timing of the steering control isperformed. Accordingly, the period for preparing the driver for the endof the steering control can be ensured, and the delivery of the steeringinitiative from the control device to the driver can be safelyperformed.

A second aspect of the disclosure relates to a control method of avehicle. The vehicle includes an electronic control unit. The controlmethod includes: executing, by the electronic control unit, steeringcontrol for avoiding a collision of a host vehicle with an object thathas a possibility of colliding with the host vehicle; setting, by theelectronic control unit, a timing when the host vehicle is predicted tobe pass the object as an end timing of the steering control when thesteering control is performed; determining, by the electronic controlunit, whether or not a deviation possibility is present when theelectronic control unit assumes that the steering control is ended atthe end timing; and performing, by the electronic control unit,reduction processing that reduces the deviation possibility when theelectronic control unit determines that the deviation possibility ispresent. The deviation possibility is a possibility of the host vehicledeviating from a current traveling lane accompanying an end of thesteering control.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the disclosure will be described below withreference to the accompanying drawings, in which like numerals denotelike elements, and wherein:

FIG. 1 is a block diagram for describing a configuration of a controldevice according to Embodiment 1;

FIG. 2 is a diagram for describing a method of specifying an avoidancetrajectory;

FIG. 3 is a diagram for describing an operation example of a hostvehicle when steering control is selected as assistance control;

FIG. 4 is a diagram for describing a trajectory of the host vehicleafter the vehicle passes an object;

FIG. 5 is a diagram for describing an example of reduction processingaccording to Embodiment 1;

FIG. 6 is a flowchart for describing an example of an assistance controlprocessing routine implemented by a driving assistance ECU in Embodiment1;

FIG. 7 is a flowchart for describing an example of a reductionprocessing routine implemented by the driving assistance ECU inEmbodiment 1;

FIG. 8 is a flowchart for describing an example of a steering controlend processing routine implemented by the driving assistance ECU inEmbodiment 1;

FIG. 9 is a diagram for describing an effect of the reduction processingaccording to Embodiment 1;

FIG. 10 is a diagram for describing an example of reduction processingaccording to a modification example of Embodiment 1;

FIG. 11 is a flowchart for describing an example of a reductionprocessing routine implemented by a driving assistance ECU in Embodiment2; and

FIG. 12 is a diagram for describing an effect by reduction processingaccording to Embodiment 2.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the disclosure will be described based ondrawings. The same reference numeral is assigned to a common element ineach drawing, and redundant description is omitted. The disclosure isnot limited to the following embodiments.

First, Embodiment 1 will be described with reference to FIGS. 1 to 10.

Configuration of Control Device for Vehicle

FIG. 1 is a block diagram for describing a configuration of a controldevice for vehicle according to Embodiment 1. The control deviceaccording to Embodiment 1 includes a driving assistance ECU 10, a brakeECU 20, a steering ECU 30, and a warning ECU 40. Each ECU includes amicrocomputer as a main part and is connected so as to be transmittableand receivable mutually through a controller area network (CAN) (notillustrated). The ECU stands for an electronic control unit. In thespecification, the microcomputer includes a central processing unit(CPU) and a storage device such as a read only memory (ROM) and a randomaccess memory (RAM), and the CPU executes an instruction (program)stored in the ROM to realize various functions. In the specification, avehicle on which the control device is mounted is also referred to as“host vehicle”.

The driving assistance ECU 10 is connected to an external sensor 51, asteering torque sensor 52, a yaw rate sensor 53, a vehicle speed sensor54, and an acceleration sensor 55. The steering torque sensor 52, theyaw rate sensor 53, the vehicle speed sensor 54, and the accelerationsensor 55 are classified as internal sensors.

The external sensor 51 has a function of acquiring information relatingto at least a road in front of the host vehicle and a solid objectpresent around the road. The solid object represents, for example, amoving object such as a pedestrian, a bicycle, and a vehicle, and afixed object such as a utility pole, a tree, and a guardrail.

The external sensor 51 includes, for example, a radar sensor and acamera sensor. The radar sensor radiates, for example, a radio wave in amillimeter wave band (hereinafter, referred to as “millimeter wave”) tothe surroundings (including at least the front side) of the hostvehicle. When a solid object reflecting the millimeter wave is presentin a radiation range, the radar sensor calculates presence or absence ofthe solid object and a relative relationship (distance between the hostvehicle and the solid object, relative speed of the host vehicle withrespect to the solid object, and the like) between the host vehicle andthe solid object by the reflected wave from the solid object. The camerasensor includes, for example, a stereo camera. The camera sensor imagesright and left scenes in front of the vehicle and calculates the shapeof a road, the presence or absence of the solid object, the relativerelationship between the host vehicle and the solid object, and the likebased on the imaged right and left image data. The camera sensorrecognizes a lane marker (hereinafter, referred to as “white line”) suchas an outside line of a roadway, a center line of the roadway, and aboundary line between a traveling lane and a passing lane to calculatethe shape of the road and a positional relationship between the road andthe host vehicle.

Information acquired by the external sensor 51 is also referred to as“target information”. The external sensor 51 repeatedly transmits thetarget information to the driving assistance ECU 10 at a predeterminedperiod. The external sensor 51 may not include the radar sensor and thecamera sensor and may include, for example, only the camera sensor.Information of a navigation system can be used for information on theshape of the road on which the host vehicle travels and informationrepresenting the positional relationship between the road and the hostvehicle.

The steering torque sensor 52 detects steering torque that a driverinputs to steered wheels and transmits a detection signal of thesteering torque to the driving assistance ECU 10. The yaw rate sensor 53detects a yaw rate applied to the host vehicle and transmits a detectionsignal of the yaw rate to the driving assistance ECU 10. The vehiclespeed sensor 54 detects a traveling speed of the host vehicle(hereinafter, referred to as “vehicle speed”) and transmits a detectionsignal of the traveling speed to the driving assistance ECU 10. Theacceleration sensor 55 detects front-rear acceleration which isacceleration applied in the front-rear direction of the host vehicle andlateral acceleration which is acceleration applied in the right and leftdirection (vehicle width direction) of the host vehicle, and transmits adetection signal of the front-rear acceleration and the lateralacceleration to the driving assistance ECU 10. The vehicle speed sensor54 may be a tire-wheel assembly speed sensor.

The brake ECU 20 is connected to a brake actuator 21. The brake actuator21 is provided in a hydraulic circuit between a master cylinder (notillustrated) that pressurizes hydraulic oil by stepping force on a brakepedal and friction brake mechanisms 22 provided on right, left, front,and rear tire-wheel assemblies. The friction brake mechanism 22 includesa brake disc 22 a fixed to the tire-wheel assembly and a brake caliper22 b fixed to a vehicle body. The friction brake mechanism 22 operates awheel cylinder embedded in the brake caliper 22 b by hydraulic pressureof the hydraulic oil supplied from the brake actuator 21 to press abrake pad against the brake disc 22 a and generates friction brakingforce.

The steering ECU 30 is a control device of an electric power steeringsystem and is connected to a motor driver 31. The motor driver 31 isconnected to a steering motor 32. The steering motor 32 is incorporatedin a steering mechanism (not illustrated), a rotor of the motor isrotated by electric power supplied from the motor driver 31, and rightand left steering tire-wheel assemblies are steered by the rotation ofthe rotor. In a normal time, the steering ECU 30 causes the steeringmotor 32 to generate steering assist torque corresponding to steeringtorque of the driver detected by the steering torque sensor 52. Adirection of the steering torque is identified by a sign (positive ornegative) of the steering torque. For example, the steering torqueacting in the right direction is represented as positive steeringtorque, and the steering torque acting in the left direction isrepresented as negative steering torque. When a steering control commandvalue (steering torque command value described below) transmitted fromthe driving assistance ECU 10 is received when the driver does notoperate a steering wheel, the steering motor 32 is driven and controlledaccording to the steering control command value to steer the steeringtire-wheel assemblies.

The warning ECU 40 is connected to a human machine interface (HMI) 41.The HMI 41 is sound output means such as a buzzer and a speaker, anddisplay means such as a head up display (HUD), a display of thenavigation system, and combination meter. The warning ECU 40 outputs awarning sound from the sound output means according to an alert commandfrom the driving assistance ECU 10 or displays a warning message, awarning lamp, and the like on the display means to notify the driver ofan operation situation of assistance control.

Configuration of Driving Assistance ECU

The driving assistance ECU 10 will be described. The driving assistanceECU 10 includes a host vehicle track determination unit 11, a solidobject detector 12, an object recognition unit (hereinafter, referred toas object recognition unit) 13 that determines an object with apossibility of a collision, an assistance control determination unit 14,a deceleration controller 15, a steering controller 16, a reductionprocessing determination unit (hereinafter, referred to as reductionprocessing determination unit) 17 that determines presence or absence ofa possibility of deviating from the traveling lane.

The host vehicle track determination unit 11 generates informationrelating to the road on which the host vehicle travels at apredetermined calculation cycle based on the target informationtransmitted from the external sensor 51. With a front end centerposition of the host vehicle as an origin point, the host vehicle trackdetermination unit 11 generates, for example, coordinate information(position information) on the ground, the solid object, and the whiteline using a coordinate system expanding in the right and leftdirection, and the front side from the origin point. As described above,the host vehicle track determination unit 11 grasps a shape of thetraveling lane of the host vehicle defined by right and left whitelines, a position and an orientation of the host vehicle within thetraveling lane, and a relative position of the solid object with respectto the host vehicle. The host vehicle track determination unit 11calculates a turning radius of the host vehicle based on the yaw ratedetected by the yaw rate sensor 53 and the vehicle speed detected by thevehicle speed sensor 54, and calculates a trajectory of the host vehiclebased on the turning radius.

The solid object detector 12 discriminates whether the solid object isthe moving object or a stationary object based on a change in a positionof the solid object. When the solid object is discriminated as themoving object, the solid object detector 12 calculates a trajectory ofthe solid object. For example, a movement speed of the solid object inthe front-rear direction (traveling direction of the host vehicle) canbe calculated from a relationship between the vehicle speed and therelative speed with respect to the solid object. A movement speed of thesolid object in the right and left direction can be calculated from achange amount of a distance between a lateral end position of the solidobject and the white line detected by the external sensor 51 and thelike. The solid object detector 12 calculates the trajectory of thesolid object based on the movement speeds of the solid object in thefront-rear direction, and the right and left direction. The solid objectdetector 12 may calculate the trajectory of the solid object based onthe calculated trajectory of the host vehicle and the distance betweenthe host vehicle and the solid object detected by the external sensor51.

The object recognition unit 13 performs determination relating to thepossibility (hereinafter, referred to as “collision possibility”) of thecollision of the host vehicle with the solid object of when the hostvehicle travels with maintaining a current traveling state based on theposition of the solid object and the trajectory of the host vehicle.When the solid object is the moving object, the object recognition unit13 calculates the trajectory of the solid object and performs thedetermination relating to the collision possibility based on thetrajectory of the solid object and the trajectory of the host vehicle.The object recognition unit 13 calculates a time to collision TTC whichis a prediction time before the host vehicle collides with the solidobject (remaining time before collision) by the following equation (1)based on a distance L₁ between the solid object and the host vehicle anda relative speed Vr₁ with the solid object.

TTC=L ₁ /Vr ₁  (1)

When the time to collision TTC is equal to or less than a collisiondetermination value TTC₁ set in advance, the object recognition unit 13determines that the collision possibility is high. When the time tocollision TTC is longer than a collision determination value TTC₂(>TTC₁) set in advance, the object recognition unit 13 determines thatthere is no collision possibility. When the time to collision TTC isbetween the collision determination value TTC₁ and the collisiondetermination value TTC₂, the object recognition unit 13 determines thatthe collision possibility is low. When the collision possibility isdetermined to be high and the collision possibility is determined to below, the object recognition unit 13 recognizes the solid object as theobject. That is, when the time to collision TTC is equal to or less thanthe collision determination value TTC₂, the object recognition unit 13recognizes the solid object as the object.

The assistance control determination unit 14 determines the presence orabsence of the recognition of the object by the object recognition unit13. When the object is recognized, the assistance control determinationunit 14 selects the assistance control for avoiding the collision withthe object and sets a start timing and an end timing of the selectedassistance control. The assistance control includes deceleration controlfor decelerating the host vehicle by intervening in the drivingoperation of the driver and steering control for controlling thesteering torque of the host vehicle by intervening in the drivingoperation of the driver.

The selection of the assistance control can be performed, for example,based on a level of the collision possibility. Specifically, when thecollision possibility is high, the assistance control determination unit14 selects the deceleration control as the assistance control. When thecollision possibility is low, the assistance control determination unit14 selects the steering control as the assistance control. Theassistance control determination unit 14 can also select a combinationof the deceleration control and the steering control as the assistancecontrol regardless of the level of the collision possibility. A methodof setting the start timing and the end timing of the selectedassistance control will be described below.

When the start timing and the end timing of the deceleration control areset, the deceleration controller 15 calculates a target deceleration fordecelerating the host vehicle. For example, a case where the object isstopped is taken as an example. When a vehicle speed (=relative speed)at a current timing is V, a deceleration of the host vehicle is a, and atime until the host vehicle stops is t, a traveling distance X until thehost vehicle stops can be represented by the following equation (2).

X=V·t+(½)·a·t ²  (2)

The time t until the host vehicle stops can be represented by thefollowing equation (3).

t=−V/a  (3)

Accordingly, the deceleration a which is needed to stop the host vehicleat a traveling distance TD can be represented by the following equation(4) by substituting equation (3) into equation (2).

a=−V ²/2TD  (4)

In order to stop the host vehicle at a distance β before the object, thetraveling distance TD may be set to a distance (L₁−β) which is obtainedby subtracting the distance β from the distance L₁ detected by theexternal sensor 51. When the object is moved, the deceleration a may becalculated using the relative speed with respect to the object.

The deceleration controller 15 sets calculated deceleration, asdescribed above, to the target deceleration. However, the decelerationthat can be generated in the host vehicle has a limit (for example,about −1 G). Therefore, when an absolute value of the calculated targetdeceleration is larger than an absolute value of an upper limit valueamax, the deceleration controller 15 sets the target deceleration to theupper limit value amax. The deceleration controller 15 transmits abraking command representing the target deceleration to the brake ECU20. As described above, the brake ECU 20 controls the brake actuator 21according to the target deceleration to generate the friction brakingforce in the tire-wheel assemblies. As described above, an automaticbrake is operated and the host vehicle decelerates.

When the start timing and the end timing of the steering control areset, the steering controller 16 calculates and specifies the avoidancetrajectory in which the host vehicle may take to avoid the collisionwith the object at a predetermined calculation cycle. FIG. 2 is adiagram for describing a method of specifying the avoidance trajectory.For example, when the host vehicle is assumed to travel within a currenttraveling lane with maintaining the current traveling state, thesteering controller 16 specifies a route A through which the hostvehicle is predicted to travel. When the host vehicle adds the maximumchange in lateral acceleration for the host vehicle to turn safelywithin the current traveling lane to current lateral acceleration, thesteering controller 16 specifies a route B through which the hostvehicle is predicted to travel.

The steering controller 16 obtains a route candidate when the lateralacceleration is changed by a constant amount in a traveling range fromthe route A to the route B. The steering controller 16 specifies atrajectory that can safely avoid the collision with an object RS byturning of a host vehicle VC and where the lateral acceleration becomesthe smallest as the avoidance trajectory based on a degree ofinterference between the route candidate and the object.

The steering controller 16 calculates a target yaw rate for causing thehost vehicle to travel along the avoidance trajectory specified asdescribed above. The steering controller 16 calculates target steeringtorque that can obtain the target yaw rate based on the target yaw rate.The steering controller 16 stores in advance a map (not illustrated) inwhich the target steering torque that increases as a variation betweenthe yaw rate detected by the yaw rate sensor 53 and the target yaw rateincreases is set and calculates the target steering torque withreference to the map. The calculation described above is performed at apredetermined calculation cycle.

When the target steering torque is calculated, the steering controller16 calculates target steering assist torque obtained by subtracting acurrent steering torque of the driver from the target steering torque.The steering controller 16 calculates a steering torque command valuethat increases toward the calculated target steering assist torque andtransmits the calculated steering torque command value to the steeringECU 30. However, the steering torque is restricted. Therefore, when thecalculated target steering assist torque (positive target steeringassist torque) is larger than an upper limit value Trmax, the steeringcontroller 16 sets the target steering assist torque to the upper limitvalue Trmax. When the calculated target steering assist torque (negativetarget steering assist torque) is smaller than a lower limit valueTrmin, the steering controller 16 sets the target steering assist torqueto the lower limit value Trmin. The steering ECU 30 controls a switchingelement of the motor driver 31 to control energization to the steeringmotor 32 such that the steering motor 32 generates steering torquehaving the magnitude of the steering torque command value according tothe steering torque command value. As described above, the steeringtire-wheel assemblies are autonomously steered, and the host vehicletravels along the avoidance trajectory.

The steering controller 16 sets the target steering torque after the endtiming of the steering control to zero. When the steering torque of thedriver increases even before the end timing, the steering controller 16sets the target steering torque to zero. The steering controller 16calculates a steering torque command value that increases or decreasestoward the set target steering torque (that is, zero) and transmits thecalculated steering torque command value to the steering ECU 30.Energization control after the end timing of the steering control isbasically the same as the energization control during a period from thestart timing to the end timing of the steering control. The steeringassist torque input to the steering motor 32 gradually increases ordecreases by the energization control.

The assistance control determination unit 14 sets various timingsrelating to notice of the assistance control. The assistance controldetermination unit 14 transmits the alert command to the warning ECU 40at a stage before the automatic brake is operated or before the steeringtire-wheel assemblies are autonomously steered. As described above, thewarning ECU 40 rings the sound output means or displays a warningmessage, a warning lamp, and the like on the display means to inform thedriver of the operation situation of the assistance control. The warningECU 40 starts or ends the operation of the sound output means and thelike at the various timings relating to the notice of the assistancecontrol based on the alert command. As described above, start notice isexecuted during a period from a timing before the start timing of theassistance control by a predetermined time to the start timing. Endnotice is executed during a period from a timing before the end timingof the assistance control by a predetermined time to the end timing.

When at least the steering control is selected as the assistancecontrol, the reduction processing determination unit 17 performsdetermination relating to the possibility (hereinafter, referred to as“deviation possibility”) that the host vehicle advances in a directionnot intended by the driver and deviates from (move out of) the currenttraveling lane after the steering control ends. Details of the reductionprocessing determination unit 17 will be described below.

Details of Assistance Control Determination Unit

Details of the assistance control determination unit 14 will bedescribed. As described already, when the object is recognized, theassistance control determination unit 14 selects at least one of thedeceleration control or the steering control as the assistance control.FIG. 3 is a diagram for describing an operation example of the hostvehicle when the steering control is selected as the assistance control.In the example illustrated in FIG. 3, the object RS is assumed to berecognized. It is assumed that the possibility of the collision of thehost vehicle VC with the object RS is determined to be low. At least thesteering control is assumed to be selected as the assistance control soas to cause the host vehicle VC to pass the object RS instead ofstopping the host vehicle VC before the object RS.

Here, when the start timing of the steering control is too early, theautonomous steering interferes with a steering wheel operation of thedriver. For example, there is a case where the autonomous steering isstarted ahead of the steering wheel operation despite a situation wherethe driver is aware of presence of the object RS and attempts to operatethe steering wheel when the object RS and the host vehicle VC come closeto each other. In the case described above, the driver may feel a senseof discomfort. In order to avoid the problem as described above, theassistance control determination unit 14 sets a timing when the hostvehicle VC is predicted to be close to the object RS to the start timingof the steering control. When the steering control is in combinationwith the deceleration control, the assistance control determination unit14 sets the start timing of the deceleration control to the same timingas the start timing of the steering control.

The assistance control determination unit 14 sets a timing when the hostvehicle VC is predicted to completely pass the object RS to the endtiming of the steering control. The timing when the host vehicle VC ispredicted to completely pass the object RS is calculated by adding anexecution period TA of the steering control to the start timing of thesteering control. The execution period TA can be represented by thefollowing equation (5) using a distance L₂ between the object RS₁ andthe host vehicle VC, a longitudinal width WRS of the object RS, and arelative speed Vr₂ with the object RS at the start timing of thesteering control.

TA=(L ₂ +WRS)/Vr ₂  (5)

When the steering control is in combination with the decelerationcontrol, the end timing of the steering control coincides with the endtiming of the deceleration control.

Details of Reduction Processing Determination Unit and Feature ofReduction Processing According to Embodiment 1

FIG. 4 is a diagram for describing a trajectory of the host vehicleafter the vehicle passes the object. In the example illustrated in FIG.4, at least the steering control is assumed to be selected as theassistance control similarly to the example illustrated in FIG. 3. Thehost vehicle VC, the object RS, and the end timing illustrated in FIG. 4are the same as those illustrated in FIG. 3. As described already, thesteering assist torque input to the steering motor 32 graduallyincreases or decreases after the end timing of the steering control.However, the current traveling lane of the host vehicle VC is curved.Therefore, when the steering torque of the driver does not change beforeand after the end timing, the host vehicle VC travels on a route Caccompanying the gradual change in the steering assist torque. Forexample, when the driver is aware of the end of the steering controlwith delay, it is expected that the steering torque of the driver doesnot change before and after the end timing. As described above, when thesteering torque of the driver after the end timing is not sufficient,there is the possibility that the host vehicle VC deviates from thecurrent traveling lane.

In view of the problem as described above, when at least the steeringcontrol is selected as the assistance control, the reduction processingdetermination unit 17 determines presence or absence of the deviationpossibility after the end timing of the steering control. The deviationpossibility is determined in consideration of, for example, host vehicletrack information such as a curvature radius R of the traveling lane anda road surface gradient, host vehicle state information such as thesteering assist torque, the lateral acceleration, and a roll angle afterthe end timing, and surrounding environment information in a deviationdirection such as a distance from a position of the host vehicle VCafter the end timing to center line CL and presence or absence ofanother vehicle traveling in an adjacent lane separated by the centerline CL. When the reduction processing determination unit 17 determinesthat there is the deviation possibility, the reduction processingdetermination unit 17 delays the end timing of the steering control setby the assistance control determination unit 14. That is, the reductionprocessing determination unit 17 postpones the end timing of thesteering control set by the assistance control determination unit 14.

When the steering control is in combination with the decelerationcontrol, the reduction processing determination unit 17 postpones theend timing of the deceleration control in accordance with thepostponement of the end timing of the steering control. As describedabove, the end timing of the deceleration control after the postponementcoincides with the end timing of the steering control after thepostponement. The end timing of the deceleration control may not bepostponed, and the deceleration control may be ended at an initially setend timing.

When the steering control is in combination with the decelerationcontrol, the deceleration controller 15 calculates the targetdeceleration (or target acceleration) for maintaining the vehicle speedat the end timing before the postponement during a period from the endtiming before the postponement to an end timing after the postponementwhen the end timing of the deceleration control is postponed.

When the end timing of the steering control is postponed, the steeringcontroller 16 calculates and specifies a trajectory (hereinafter,referred to as “trajectory during the postponement”) for the hostvehicle to travel within the current traveling lane during the periodfrom the end timing before the postponement to the end timing after thepostponement at a predetermined calculation cycle. FIG. 5 is a diagramfor describing an example of reduction processing according toEmbodiment 1. In the example illustrated in FIG. 5, at least thesteering control is assumed to be selected as the assistance controlsimilarly to the examples illustrated in FIGS. 3 and 4. The host vehicleVC and the object RS illustrated in FIG. 5 are the same as thoseillustrated in FIGS. 3 and 4. The end timing (before postponement)illustrated in FIG. 5 corresponds to the end timing illustrated in FIGS.3 and 4.

In the example illustrated in FIG. 5, a trajectory for maintaining thedistance from the position of the host vehicle VC at the end timingbefore the postponement of the steering control to the center line CLduring the postponement of the end timing is specified as the trajectoryduring the postponement. The steering controller 16 calculates a targetyaw rate for causing the host vehicle VC to travel along the trajectoryduring the postponement. The steering controller 16 calculates targetsteering torque that can obtain the target yaw rate based on the targetyaw rate. When the target steering torque is calculated, the steeringcontroller 16 calculates target steering assist torque obtained bysubtracting a current steering torque of the driver from the targetsteering torque. The steering controller 16 calculates a steering torquecommand value that increases or decreases toward the calculated targetsteering assist torque and transmits the calculated steering torquecommand value to the steering ECU 30. The steering ECU 30 controls theenergization to the steering motor according to the steering torquecommand value. As described above, the steering tire-wheel assembliesare autonomously steered, and the host vehicle VC travels along thetrajectory during the postponement.

When the end timing of the steering control is postponed, the reductionprocessing determination unit 17 updates a start timing of the endnotice of the steering control and transmits the alert command to thewarning ECU 40. The warning ECU 40 starts ringing or the like of thesound output means as the end notice of the steering control from atiming before the end timing before the postponement of the steeringcontrol by a predetermined time based on the alert command. The warningECU 40 ends the ringing or the like of the sound output means as the endnotice thereof at an end timing after the postponement of the steeringcontrol based on the alert command.

Specific Processing in Embodiment 1

FIG. 6 is a flowchart for describing an example of an assistance controlprocessing routine implemented by the driving assistance ECU 10 inEmbodiment 1. FIG. 7 is a flowchart for describing an example of areduction processing routine implemented by the driving assistance ECU10 in Embodiment 1. FIG. 8 is a flowchart for describing an example of asteering control end processing routine implemented by the drivingassistance ECU 10 in Embodiment 1. The processing routines describedabove are repeatedly implemented at a predetermined calculation cyclewhile an ignition switch is on.

When the processing routine illustrated in FIG. 6 is activated, thedriving assistance ECU 10 first determines whether the object isrecognized (step S10). The recognition processing of the object is asdescribed in the description of the object recognition unit 13. When thedriving assistance ECU 10 determines that the object is not recognized,the driving assistance ECU 10 exits the processing routine.

In step S10, when the driving assistance ECU 10 determines that theobject is recognized, the driving assistance ECU 10 selects theassistance control (step S12) and sets at least one of the start timingor the end timing of the selected assistance control (step S14). Theselection processing of the assistance control and the settingprocessing such as the start timing of the selected assistance controlare as described in the description of the assistance controldetermination unit 14.

Following step S14, the driving assistance ECU 10 sets at least one ofthe target steering assist torque or the target deceleration (step S16).A reason for setting at least one of the target steering assist torqueor the target deceleration is that at least one of the decelerationcontrol or the steering control is selected in step S14. The settingprocessing of the target deceleration is as described in the descriptionof the deceleration controller 15. The setting processing of the targetsteering assist torque is as described in the description of thesteering controller 16.

Following step S16, the driving assistance ECU 10 executes at least oneof transmitting of the steering torque command value to the steering ECU30 such that the steering control starts from the start timing set instep S14 or transmitting of the braking command to the brake ECU 20 suchthat the deceleration control starts from the same start timing (stepS18).

Following step S18, the driving assistance ECU 10 sets the start timingsof the start notice and the end notice of the assistance control andtransmits the start timings to the warning ECU 40 (step S20). Thesetting processing of the start timings of the start notice and the endnotice of the assistance control is as described in the description ofthe assistance control determination unit 14.

When the processing routine illustrated in FIG. 7 is activated, thedriving assistance ECU 10 first determines whether the end timing of thesteering control comes (step S22). The determination in step S22 isperformed based on whether the end timing of the steering control is setand whether the timing of the determination processing is earlier thanthe end timing of the steering control. When the end timing of thesteering control is not set or the timing of the determinationprocessing elapses the end timing, the driving assistance ECU 10determines that the end timing does not come. When the drivingassistance ECU 10 determines that the end timing of the steering controldoes not come, the driving assistance ECU 10 exits the processingroutine.

In step S22, when the driving assistance ECU 10 determines that the endtiming of the steering control comes, the driving assistance ECU 10performs the determination relating to the deviation possibility afterthe end timing of the steering control (step S24). The determinationprocessing relating to the deviation possibility is as described in thedescription of the reduction processing determination unit 17. When thedriving assistance ECU 10 determines that there is no deviationpossibility, the driving assistance ECU 10 exits the processing routine.

In step S24, when the driving assistance ECU 10 determines that there isthe deviation possibility, the driving assistance ECU 10 postpones theend timing of the steering control (step S26). Following step S26, thedriving assistance ECU 10 sets at least the target steering assisttorque during the postponement of the end timing (step S28). The reasonfor setting at least the target steering assist torque is that thesteering control is performed alone or in combination with thedeceleration control. When the steering control is in combination withthe deceleration control, the target deceleration is set in addition tothe target steering assist torque in step S26. Following step S28, thedriving assistance ECU 10 transmits at least the steering torque commandvalue during the postponement of the end timing to the steering ECU 30(step S30). A series of pieces of processing in steps S26 to S30 isdescribed in the description of the reduction processing determinationunit 17 and FIG. 5.

When the processing routine illustrated in FIG. 8 is activated, thedriving assistance ECU 10 first determines whether the end timing of thesteering control comes (step S32). The determination processing in stepS32 is basically the same processing as step S22 of FIG. 7. However,when the driving assistance ECU 10 delays the end timing of the steeringcontrol in step S26 of FIG. 7, the determination in step S32 isperformed based on whether the timing of determination processing isearlier than the end timing of the steering control after thepostponement.

In step S32, when the driving assistance ECU 10 determines that the endtiming of the steering control comes, the driving assistance ECU 10determines whether the steering torque of the driver increases (stepS34). When the driving assistance ECU 10 determines that the steeringtorque (positive steering torque or negative steering torque) of thedriver does not increase, determination can be made that the driverneeds to continue the steering control, the end notice of the steeringcontrol is not yet issued, or the driver is not aware of the end noticeof the steering control. Therefore, the driving assistance ECU 10 exitsthe processing routine. In order to enhance the accuracy of thedetermination in step S34, the determination relating to the steeringtorque of the driver may be in combination with determination relatingto the line of sight of the driver using an in-vehicle camera.

In step S34, when the driving assistance ECU 10 determines that thesteering torque of the driver increases, determination can be made thatthe driver indicates intention of the steering wheel operation.Therefore, the driving assistance ECU 10 transmits the steering torquecommand value for ending the steering control to the steering ECU 30(step S36). The processing in step S36 is as described in thedescription of the steering controller 16.

Following step S36, the driving assistance ECU 10 transmits a cancelcommand for canceling the start timing of the end notice of the steeringcontrol set in step S20 of FIG. 6 to the warning ECU 40 (step S38). Whenthe cancel command is issued, the end notice of the steering control bythe warning ECU 40 is not performed.

Effect of Reduction Processing According to Embodiment 1

FIG. 9 is a diagram for describing an effect of the reduction processingaccording to Embodiment 1. The various timings relating to the steeringcontrol are drawn in FIG. 9. A difference between the upper row and thelower row of FIG. 9 is presence or absence of the execution of thereduction processing. As being understood by comparing lengths of arrowsin the upper row and the lower row of FIG. 9, when the reductionprocessing is executed, the end timing of the steering control ispostponed. Accordingly, the deviation of the host vehicle from thecurrent traveling lane is suppressed. When the reduction processing isexecuted, the end timing of the end notice of the steering control isalso postponed. Accordingly, a period for preparing the driver for theend of the steering control is ensured, and delivery of steeringinitiative from the control device to the driver is safely performed.Accordingly, the deviation possibility after the end of the steeringcontrol is further reduced.

A modification example of Embodiment 1 will be described. The controldevice according to Embodiment 1 extends the steering control and theexecution period of the end notice of the steering control in thereduction processing. However, the execution period of the end notice ofthe steering control may not be extended. This is because the deviationof the host vehicle from the current traveling lane can be suppressedwith a high probability regardless of the extension of the executionperiod of the end notice of the steering control when the executionperiod of the steering control is extended. In the reduction processingaccording to the modification example, when the end timing of thesteering control is postponed, the reduction processing determinationunit 17 transmits the alert command to the warning ECU 40. The warningECU 40 starts the operation of the sound output means or the like as theend notice of the steering control from a timing before the end timingafter the postponement of the steering control by a predetermined timebased on the alert command.

In the reduction processing, the control device according to Embodiment1 specifies the trajectory for maintaining the distance from theposition of the host vehicle VC at the end timing before thepostponement of the steering control to the center line CL during thepostponement of the end timing as the trajectory during the postponement(refer to FIG. 5). However, the trajectory during the postponement isnot limited to the trajectory illustrated in FIG. 5. FIG. 10 is adiagram for describing an example of the reduction processing accordingto the modification example of Embodiment 1. In the modification exampleillustrated in FIG. 10, at least the steering control is assumed to beselected as the assistance control similarly to the example illustratedin FIG. 5. The host vehicle VC and the object RS illustrated in FIG. 10are the same as those illustrated in FIG. 5. The end timing (beforepostponement) and the end timing (after postponement) illustrated inFIG. 10 are the same as the end timings illustrated in FIG. 5.

As being understood by comparing two trajectories during thepostponement illustrated in FIG. 10, the trajectory during thepostponement according to the modification example is positioned nearthe center line CL compared with the trajectory during the postponementaccording to Embodiment 1. This is because the trajectory during thepostponement is set with the position of the host vehicle VC at the endtiming after the postponement of the steering control as the reference.Specifically, in the modification example, the distance from theposition of the host vehicle VC at the end timing of the steeringcontrol to the center line CL is set as a reference distance, and atrajectory connecting the position of the host vehicle VC and a positionof the host vehicle VC at the end timing before the postponement withinthe current traveling lane is set as the trajectory during thepostponement. As described above, during the postponement of the endtiming, various modifications can be employed in the trajectory duringthe postponement as long as a trajectory is set to maintain a distancefrom a boundary line on a deviation side of the current traveling laneto the host vehicle VC to be equal to or larger than a predetermineddistance.

The control device according to Embodiment 1 calculates the steeringtorque (target steering torque, target steering assist torque, andsteering torque command value) as a control amount for steering thesteering tire-wheel assemblies. However, the control device maycalculate a steering angle (target steering angle, target steeringassist angle, and steering angle command value) instead of the steeringtorque. In the case, for example, assuming that a steering angle neutralpoint is 0°, the steering angle when the steering tire-wheel assembliesare rotated in the right direction from the steering angle neutral pointcan be represented as a positive value, and the steering angle when thesteering tire-wheel assemblies are rotated in the left direction can berepresented as a negative value. The modification can be similarlyemployed in Embodiment 2 described next.

Embodiment 2 will be described with reference to FIGS. 11 and 12. Sincea configuration of the control device according to Embodiment 2 iscommon to the configuration of Embodiment 1, the description of theconfiguration will be omitted.

Feature of Reduction Processing According to Embodiment 2

The control device according to Embodiment 1 postpones the end timing ofthe steering control while the device executes the reduction processingthat maintains the start timing of the end notice of the steeringcontrol at the start timing before the postponement. The control devicefor the vehicle according to Embodiment 2 does not postpone the endtiming of the steering control while the device executes the reductionprocessing that advances the start timing of the end notice of thesteering control earlier than the initially set timing.

In the reduction processing according to Embodiment 2, when thereduction processing determination unit 17 determines that there is thedeviation possibility, the reduction processing determination unit 17advances the timing of the end notice of the steering control. Theassistance control determination unit 14 transmits the alert command tothe warning ECU 40 at the stage before the steering tire-wheelassemblies are autonomously steered. The warning ECU 40 starts or endsthe operation of the sound output means or the like based on the alertcommand. As described above, the end notice of the steering control isexecuted during the period from the timing earlier than the initiallyset timing to the end timing of the assistance control.

FIG. 11 is a flowchart for describing an example of the reductionprocessing routine implemented by the driving assistance ECU 10 inEmbodiment 2. When the processing routine of FIG. 7 is replaced with theprocessing routine illustrated in FIG. 11, the assistance controlprocessing routine according to embodiment 2 is described.

The processing routine illustrated in FIG. 11 differs from theprocessing routine illustrated in FIG. 7 only in processing when adetermination result in step S24 is positive. That is, in step S24, whenthe reduction processing determination unit 17 determines that there isthe deviation possibility, the driving assistance ECU 10 advances thestart timing of the end notice of the steering control and transmits theadvanced start timing to the warning ECU 40 (step S40).

FIG. 12 is a diagram for describing an effect by the reductionprocessing according to Embodiment 2. The various timings relating tothe steering control are drawn in FIG. 12. A difference between theupper row and the lower row of FIG. 12 is the presence or absence of theexecution of the reduction processing. As being understood by comparinglengths of arrows in the upper row and the lower row of FIG. 12, whenthe reduction processing is executed, the start timing of the steeringcontrol is advanced. Accordingly, a period for preparing the driver forthe end of the steering control is ensured, and the delivery of steeringinitiative from the control device to the driver is safely performed.Accordingly, the deviation possibility after the end of the steeringcontrol is further reduced.

What is claimed is:
 1. A control device for a vehicle, the controldevice comprising: an external sensor that detects an object outside thevehicle; and a driving assistance electronic control unit programmed to:determine whether or not the vehicle has a possibility of colliding withthe object; based upon the determination that the vehicle has thepossibility of colliding with the object, select a driving assistancecontrol for avoiding collision of the vehicle with the object, whereinthe driving assistance control includes at least one of a decelerationcontrol or a steering control; set a time period for executing thedriving assistance control; execute the driving assistance control;during execution of the driving assistance control and before thevehicle passes the object, determine whether or not a deviationpossibility is present of the vehicle deviating from a current travelinglane at a point when the vehicle is predicted to pass the object; andextend the time period for executing the driving assistance control whenthe electronic control unit determines that the deviation possibility ispresent.
 2. The control device according to claim 1, wherein, when thetime period for executing the driving assistance control is extended,the electronic control unit causes the vehicle to travel along atrajectory that maintains a distance, from a boundary line on adeviation side of the current traveling lane to the vehicle, to be equalto or larger than a predetermined distance.
 3. The control deviceaccording to claim 2, wherein: the electronic control unit is furtherprogrammed to control an interface of the vehicle to notify a driver ofthe vehicle, at a predetermined time before the extended time periodends, that the driving assistance control will end.
 4. A control methodof a vehicle including an electronic control unit, the methodcomprising: detecting, by an external sensor, an object outside thevehicle; determining, by the electronic control unit, whether or not thevehicle has a possibility of colliding with the object; selecting, bythe electronic control unit, a driving assistance control for avoidingcollision of the vehicle with the object, wherein the driving assistancecontrol includes at least one of a deceleration control or a steeringcontrol; setting, by the electronic control unit, a time period forexecuting the driving assistance control; executing, by the electroniccontrol unit, the driving assistance control; during execution of thedriving assistance control and before the vehicle passes the object,determining, by the electronic control unit, whether or not a deviationpossibility is present of the vehicle deviating from a current travelinglane at a point when the vehicle is predicted to pass the object; andextending, by the electronic control unit, the time period for executingthe driving assistance control when the electronic control unitdetermines that the deviation possibility is present.
 5. The controlmethod according to claim 4, wherein, based upon the time period forexecuting the driving assistance control being extended, causing thevehicle to travel along a trajectory that maintains a distance, from aboundary line on a deviation side of the current traveling lane to thevehicle, to be equal to or larger than a predetermined distance.
 6. Thecontrol method according to claim 5, further comprising controlling aninterface of the vehicle to notify a driver of the vehicle, at apredetermined time before the extended time period ends, that thedriving assistance control will end.